Solve day 1

input/day01_test1.txt

@@ -0,0 +1,14 @@
+1000
+2000
+3000
+
+4000
+
+5000
+6000
+
+7000
+8000
+9000
+
+10000

src/day01.zig

@@ -1,17 +1,64 @@
 const std = @import("std");
 
-pub fn solve_part1() !u32 {
-    return 0;
+const MAX_BYTES = 2048 * 2048;
+
+var gpa = std.heap.GeneralPurposeAllocator(.{ .safety = true }){};
+const allocator = gpa.allocator();
+
+pub fn solve_part1(filename: []const u8) !usize {
+    const input_file = try std.fs.cwd().openFile(filename, .{ .mode = std.fs.File.OpenMode.read_only });
+    defer input_file.close();
+
+    const input = try input_file.readToEndAlloc(allocator, MAX_BYTES);
+    defer allocator.free(input);
+
+    var lines = std.mem.split(u8, input, "\n");
+    var largest_calories: usize = 0;
+    var calories: usize = 0;
+    while (lines.next()) |line| {
+        if (std.mem.eql(u8, line, "")) {
+            calories = 0;
+        } else {
+            calories += try std.fmt.parseInt(usize, line, 10);
+        }
+
+        if (calories > largest_calories) {
+            largest_calories = calories;
+        }
+    }
+    return largest_calories;
 }
 
-pub fn solve_part2() !u32 {
-    return 0;
+pub fn solve_part2(filename: []const u8) !usize {
+    const input_file = try std.fs.cwd().openFile(filename, .{ .mode = std.fs.File.OpenMode.read_only });
+    defer input_file.close();
+
+    const input = try input_file.readToEndAlloc(allocator, MAX_BYTES);
+    defer allocator.free(input);
+
+    var lines = std.mem.split(u8, input, "\n");
+    var elves = std.ArrayList(usize).init(allocator);
+    defer elves.deinit();
+    var calories: usize = 0;
+    while (lines.next()) |line| {
+        if (std.mem.eql(u8, line, "")) {
+            try elves.append(calories);
+            calories = 0;
+        } else {
+            calories += try std.fmt.parseInt(usize, line, 10);
+        }
+    }
+
+    var elves_slice = elves.toOwnedSlice();
+    defer allocator.free(elves_slice);
+    std.sort.sort(usize, elves_slice, {}, comptime std.sort.desc(usize));
+    return elves_slice[0] + elves_slice[1] + elves_slice[2];
 }
 
 test "solves part1" {
-    try std.testing.expectEqual(solve_part1(), 0);
+    try std.testing.expectEqual(solve_part1("input/day01_test1.txt"), 24000);
 }
 
 test "solves part2" {
-    try std.testing.expectEqual(solve_part2(), 0);
+    try std.testing.expectEqual(solve_part2("input/day01_test1.txt"), 45000);
 }

src/main.zig

@@ -7,7 +7,10 @@ pub fn main() !void {
     var bw = std.io.bufferedWriter(stdout_file);
     const stdout = bw.writer();
 
-    try stdout.print("Day 1\nPart 1: {}\nPart 2: {}\n\n", .{ try day01.solve_part1(), try day01.solve_part2() });
+    try stdout.print("Day 1\nPart 1: {}\nPart 2: {}\n\n", .{
+        try day01.solve_part1("input/day01.txt"),
+        try day01.solve_part2("input/day01.txt"),
+    });
 
     try bw.flush();
 }